It is known that increasing the damping in a structure will result in the improvement in the response and performance of a structure under earthquake vibrations, wind forces or any structural stability hazard of similar nature. All structures have inherent damping which causes them to stop vibrating. This damping is the result of internal factors such as damping of the material of the structure, the movement in the connections or external factors such as air resistance. Typically damping in a structure can approximately vary between 2% to 7%. With the use supplemental dampers, damping can be increased substantially to a desirable value of 15% to 25% or more. With the use of supplemental dampers, the damping of vibrations due to any structural stability hazard such as undesirable vibrations caused by an earthquake can be further mitigated. More particularly, with the use of supplemental dampers, damping can be increased substantially to a desirable value of 15% to 25% or more.
Among the different kinds of structural damping systems, solid viscoelastic dampers due to their inherent advantages, have been extensively studied for uses in relation to the protection of buildings against vibration and lateral movement (Housener, 1997). Rubber is usually the solid viscoelastic material employed in damper systems used for base isolation in buildings to protect superstructures against ground shaking (Islam, A. 2013, Gueguen, P. 2012) or in machine foundations to diminish in exemplary cases, engine vibrations (Chehab, 2003). Rubber has also been known to be utilized in seismic isolation pads that provide for the decoupling between a building and a foundation.
As mentioned before, rubber materials are mostly used as base isolations in foundations of buildings, but in recent research studies, new kinds of viscoelastic dampers have been proposed which are used as wall dampers. Ibrahim et. al. (2007) investigated a new viscoelastic damping device which consists of a block of a high damping rubber sandwiched between steel plates which provided additional energy dissipation. Cho and Kwon (2004) proposed a system to improve the performance of reinforced concrete (RC) frame structures under earthquake loads. The wall-type damper has an advantage in the retro-fit of RC structures. The system consists of a Teflon slider and a RC wall (i.e. a friction type damper). The damper is also designed to control normal pressures acting on a frictional slider. The damper as proposed by Cho and Kwon (2004) appears to be effective in mitigating seismic responses of RC frame structures and reducing damage to RC structural members. Experimental results suggests that use of friction type dampers as proposed by Cho and Kwon (2004), can not only reduce structural seismic responses but can also prevent stress concentrations which usually take place at the connection between brace-type dampers and its joining RC members. However, owing to the inherent characteristics of friction dampers, the friction wall damper is not suitable for alleviating wind-induced or low intensity earthquake excited structural responses.
Studies on viscoelastic wall type dampers appear to suggest that similar to ordinary viscoelastic dampers, the performance of viscoelastic wall type dampers are also affected by factors that include variance in environmental temperature and strain amplitude of the viscoelastic material layer. Accordingly, thus far, an efficient control effect cannot always be achieved. In contrast, viscous wall type dampers, appear to provide a better option when taking into consideration wind and seismic response control of building structures.
In accordance to the state of the art, it appears that a lot of research has focused on the development of viscous wall dampers as opposed to viscoelastic wall damper devices. Due to a readily available supply of rubber, it may be advantageous to develop a viscoelastic wall panel damping device that utilizes rubber as the viscoelastic damping element. It may further be advantageous to develop a viscoelastic wall panel damping device that exhibits appreciable wind and seismic response control.